from machine import Pin
import time

led18 = Pin(18, Pin.OUT)
led16 = Pin(16, Pin.OUT)
led17 = Pin(17, Pin.OUT)


while True:  
    led18.value(1)
    led16.value(0)
    led17.value(0)
    time.sleep(0.5)
    led18.value(0)
    led16.value(1)
    led17.value(0)
    time.sleep(0.5)
    led18.value(0)
    led16.value(0)
    led17.value(1)
    time.sleep(0.5)
